1. Field of Invention
This invention relates generally to support systems for concrete formwork and more particularly to a support system and related bracket for formwork for casing a crown on a top end of a concrete structural column of a highway bridge.
2. Prior Art
As is well known, use of concrete as a building material concurrently requires formwork to hold and shape just poured concrete until that concrete is sufficiently cured to allow removal of the formwork. Until formwork removal, the curing concrete and formwork must be secured by a formwork support system.
One early concrete formwork support system is disclosed in U.S. Pat. No. 3,504,879. This system includes a bracket attachable to a side to a structural column of a building under construction to support the formwork needed for casting an above floor of the building. This bracket has a vertical tubular body formed with internal threading for disposition of a vertically positioned jack screw. An upper end of the jack-screw has an internal bore to rotatably receive a pin attached to a bottom side of a horizontally positioned, channel-shaped support head. Extending horizontally inward from the body is a pair of spaced apart upper and lower projections. These projections include respective passages to receive a pair of mounting bolts that extend outward from the column. Attached to an outer end of the upper projection is a horizontally positioned roller.
For use, the bracket is attached to the column using the mounting bolts. A bottom beam of the formwork then is positioned in the support head, and the formwork raised to a desired location by rotating the jack-screw. When the concrete poured onto the formwork has set, the formwork may be lowered by rotating the jack-screw in a reverse direction until the formwork beam rests on the bracket roller. The formwork then may be rolled out from under the now semi- cured concrete floor above.
A further bracket for a concrete formwork support system is disclosed in U.S. Pat. No. 3,863,877. This bracket comprises a column-attached support part and a movable jack part. The jack part then includes a base plate that operatively carrying a vertically positioned jack- screw. On an upper end of the jack-screw is a frame that supports a pair of rollers. Each roller has a cylindrical traction section and connecting spool-shaped flange. Attached to respective side edges of the jack part base plate is pair of inward facing channels. Slidably disposed in these channels are respective side edges of a pair of spaced apart shelf arms of the bracket support part. The arms in turn are attached to respective top edges of a pair of triangular shaped gusset plates that then are attached to a vertically positioned backing plate. This backing plate is prepared to be attached to a side of a structural column of a building under construction.
A laterally adjustable bracket for shoring concrete formwork is set out in U.S. Pat. No. 3,967,806. This bracket includes a horizontally positioned, angle-shaped arm having an inner end joined to a vertically positioned end plate attachable to a side of a concrete column of a building under construction. This bracket further includes a vertically positioned plate member formed with an inverted L-shaped opening for disposition of the angle-shape arm. Attached to an outer side of the plate are spaced apart, upper and lower projections of a jack-screw unit having a vertical cylindrical portion to operatively receive a jack-screw. A support head is attached to a top end of the jack-screw. On an outer end of the upper projection is a pair of spaced apart lugs to hold ends of a shaft for a horizontally positioned roller. The plate member and attached jack- screw unit may slide laterally along the bracket angle arm until the support head is properly aligned with the formwork above. The location of the plate member and jack-screw unit then are secured in place by inward threading of a fastener carried by one of a pair of spaced apart ears on the plate member. These ears are positioned on respective sides of a vertical leg of the angle arm.
Other examples of formwork support systems are disclosed in U.S. Pat. Nos. 3,797,794; 3,815,858; 3,900,179; and 4,768,939.